| Gas separation membrane technology,as a green technology,has been developed rapidly in recent years.Polymeric membranes are limited widely application in the area of gas separation because they can't exceed the Robesen upper bound.Novel functional membrane materials—carbon membranes were found in the 1960s,which showed great potential in the area of gas separation for their super microporous distinguishing size of gas molecules,good thermal and chemical resistance.However,they are still commercially unavailable because of some problems,i.e.high-cost,low gas permeance and poor mechanism.Therefore,it is urgent to develop cheap precursors with good performance,optimize preparation technology, improve gas permeate and prepare supported carbon composite membranes and solve the problem in the field of carbon membranes.In this paper,novel cheaper poly(phthalazinone ether sulfone ketone)(PPESK),with China's independently intellectual property rights,has been developed to prepare carbon membranes for gas separation.Coal-based carbon tube with low cost was used as the support to prepare carbon composite membranes.It is an important approach to design the technology route to prepare the carbon membranes with high performance.As a kind of thermoplastic polymer,preoxidation is an effective method to ensure the structure stabilization of PPESK.The behaviors of thermal decomposition and cross-linking of PPESK during preoxidation were characterized by TG,FTIR,XRD,EA and NMR,and the preoxidation mechanism was concluded.The results showed that the preoxidation of PPESK was a free radicals reaction,which was initiated by the decomposition of proton in aromatic ring and sulfone functional group and the removal of H2O and SO2.When the preoxidation temperature was above 460℃,the radical reaction was initiated by the decomposition of ketone functional group and the removal of CO2.At last,the three-demensional cross-linking structure containing polyaromatic ether and biphenyl was formed.PPESK was transformed from thermoplasticity to thermoset.The optimum preoxidation conditions are the temperature at 460℃and the duration time at 30min.The PPESK-based carbon membranes were prepared by preoxidation of the polymeric membranes in air and then carbonization the oxidized membranes in argon.The effect of preoxidation and carbonization conditions on the microstructure and gas separation was investigated.It was found that gas permeability and ideal separation factor of the carbon membranes can be controlled by optimizing the experimental conditions.The results showed that the carbon membranes preoxidized at 460℃,30min,and carbonized at 650℃reached the highest permeability.The permeabilities of H2,CO2,O2,N2 were 1016.4,710.3,187.8,14.0 Barrer(1 Barrer=10-10cm3(STP)·cm·cm2·s-1·cmHg-1),respectively.The carbon membranes preoxidized at 460℃,30 min,and carbonized at 850℃reached the highest selectivity.The ideal separation factors of H2/N2,CO2/N2,O2/N2 were 129.2,93.1,21.9,respectively.The derived carbon membranes were used to enrich the O2 in air,and the O2 concentration can reach 86.4%.The carbon membranes were modified by blending Zeolite Beta in PPESK to improve the gas permeate and the trade-off of selectivity and permeability.When the weight ratio of Beta/PPESK was lower,the selectivity and permeability of the carbon membranes were increased at the same time.However,when the weight ratio of Beta/PPESK was higher,the permeability of the carbon membranes was increased and the selectivity was decreased obviously.With the increase of the weight ratio of Beta/PPESK from 0.1 to 0.2,the permeabilities of H2,CO2,O2 and N2 reached 2313.3,1566.8,276.5,31.9 barrer,respectively.The technology route to prepare the carbon composite membranes with high performance was designed.The supported carbon composite membranes were prepared by coating the solution of PPESK blended with poly(ethylene glycol)(PEG)on the cheaper coal-based carbon tubular supports.The results showed that PEG had the functions of improving the composite performance between PPESK and carbon tube and increasing porosity of the carbon composite membranes.The PEG/PPESK based carbon composite membranes with molecular sieving needed dip-coating only one time.Compared with the PPESK-based carbon composite membranes,the PEG/PPESK based carbon composite membranes had good permeation and selectivity.The ideal separation factors of H2/N2 and O2/N2 reached 40～105 and 4～14,respectively.The permeation rates of H2 and O2 were 0.075～0.75 MPU and 0.01～0.08 MPU(1 MPU=1×10-8mol·m-2·s-1·Pa-1),respectively.Compared with the carbon composite membranes derived from other precursors,the PEG/PPESK based carbon composite membranes reduced preparation costs and increased gas separation performance,which would have good prospects in industrial applications.
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